My first aquaponics system was a joy to construct and has pretty much worked exactly as it should. There were few trials along the way and for the most part I really only had to make one alteration to my original design. It is a traditional flood and drain aquaponics system based on a 500 litre fish tank and 250 litre grow bed. This system can comfortably hold 25 fish and grow them to over 1kg in size which is suitable for the table. The components list is-

• 500 litre water tank with removable lid
• 250 litre guppy tank for the growbed
• 1000 litre per hour aquarium pump
• 13mm (1/2") tub inlet with screen
• 100cm 13mm pipe for inlet pipe
• 200cm 25mm (1") PVC pipe for outlet pipe
• 3 X 25mm PVC 90 degree elbows
• 25mm PVC tub outlet
• 1500 litre per hour aquarium air pump
• 6 metres of air hose
• 1 air stone
• Timer for pump cycles
• Home made welded steel grow bed stand

The 500 litre fish tank is actually a rain water tank purchased from a large hardware store chain during a sale. The tank was marked down considerably in price and was such a bargain that I purchased two because I was keenly aware that I was not going to get another at that price. One of its best features is the removable lid, allowing the fish to be out of direct sunlight and more importantly keeping our little coastal towns pelican population from getting an easy meal.

The growbed is a guppy breeding tank that was lying unused for years in our garden shed after being purchased for use as a hydroponic nutrient tank. I also grow vegetables hydroponically and at one point this tank provided a central reservoir for a large top feed hydroponic system. It is filled with ordinary gravel purchased from a landscape supplier but in future I suspect I'll look at using hydroclay for my media instead as it is lighter and has a larger particle size. This growbed weighs over 1/4 ton when filled! The stand that the growbed sits on was contructed specifically for it as I had a spare length of steel cluttering up the backyard from another project. Your growbed stand must be strong but not necessarily made out of steel, concrete blocks or bricks and railway sleepers for example will make a strong growbed stand. Make sure your growbed sits level.

The original return pipe for the growbed was made from 19mm (3/4") flexible tubing that I have always used on my hydroponics systems. My aquaponics system has a larger pump with a higher flowrate and the volume of water being returned is higher than any of my hydroponics systems. This was not a problem until we suffered a heatwave and the flexible pipe got soft, sucked itself closed and caused the system to overflow. Fortunately I was home at the time and noticed. The flexible pipe was immediately replaced by 25mm (1") PVC pipe and the problem was resolved. The inlet pipe is still 13mm flexible as the pump delivers the water under pressure and this problem cannot occur.

This aquaponics system was originally an experiment to see what aquaponics is all about. The system produces a steady supply of organic vegetables that taste just great and the fish are progressing very well as of time of writing and we look forward to delicious natural fish soon as well. We're really hooked on aquaponics. Plans are already on the drawing board to reduce our number of hydroponic systems and replace them with aquaponics systems.